1. Field of the Invention
The present invention relates generally to the field of information storage devices, and more particularly to suspension assemblies used in head gimbal assemblies of such devices.
2. Background of the Art
Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write, but other information storage devices also include heads—sometimes including heads that cannot write.
In a modern magnetic hard disk drive device, each head is a sub-component of a head gimbal assembly (HGA) that typically includes a suspension assembly with a laminated flexure to carry the electrical signals to and from the head. The HGA, in turn, is a sub-component of a head stack assembly (HSA) that typically includes a plurality of HGAs, an actuator, and a flex cable. The plurality of HGAs are attached to various arms of the actuator, and each of the laminated flexures of the HGAs has a flexure tail that is electrically connected to the HSA's flex cable.
Modern laminated flexures typically include conductive copper traces that are isolated from a stainless steel structural layer by a polyimide dielectric layer. So that the signals from/to the head can reach the flex cable on the actuator body, each HGA flexure includes a flexure tail that extends away from the head along the actuator arm and ultimately attaches to the flex cable adjacent the actuator body. That is, the flexure includes traces that extend from adjacent the head and terminate at electrical connection points at the flexure tail. The flex cable includes electrical conduits that correspond to the electrical connection points of the flexure tail.
Since the conductive traces are separated from the structural layer by a dielectric layer, electrical capacitance exists between the conductive traces and the structural layer, and this affects the capacitive reactance and impedance of the conductive traces. Since the dielectric layer is most practically of nearly constant thickness, the most practical way to control or change the capacitance between the conductive traces and the structural layer is to control or change the area of overlap, which can be done by etching apertures/windows into the underlying structural layer. However such apertures in the structural layer also affect the structural characteristics of the flexure tail (e.g. flexure tail stiffness, stress concentration regions, yielding, and strength). Therefore, there is a need in the art for an aperture arrangement for the structural layer in flexure tails that may allow impedance control while limiting adverse consequences on the structural characteristics of the flexure tail.